Supporting a surveillance of positions of devices

ABSTRACT

Each of a plurality of transmitters, which are distributed at fixed locations of a site, regularly transmits radio signals. A mesh node performs measurements on radio signals transmitted by at least one transmitter and transmits messages including results of the measurements. The mesh node belongs to a plurality of mesh nodes, each configured to monitor at least one environmental parameter at the site. A gateway node receives messages transmitted by the mesh node directly and/or via at least one other mesh node of the plurality of mesh nodes, wherein each of the plurality of mesh nodes is configured to receive messages from other mesh nodes of the plurality of mesh nodes and to forward received messages. The gateway node transmits received messages to a server that is configured to monitor mesh nodes at the site based on results of measurements.

This application is a continuation under 35 U.S.C § 120 and 37 C.F.R. §1.53(b) of U.S. patent application Ser. No. 15/420,312 filed Jan. 31,2017, the disclosure of which is incorporated herein by reference in itsentirety.

FIELD OF THE DISCLOSURE

The disclosure relates to the field of positioning and more specificallyto supporting a surveillance of positions of devices at a particularsite.

BACKGROUND

Satellite signal based positioning technologies, which are mainly usedoutdoors, are usually not suited to deliver a satisfactory performancewhen used for indoor positioning, since satellite signals of globalnavigation satellite systems (GNSS), like the global positioning system(GPS), do not penetrate through walls and roofs strongly enough for anadequate signal reception indoors. Thus, these positioning technologiesare not able to deliver a performance indoors that would enableseamless, equal and accurate positioning outdoors and indoors.

Therefore, several dedicated solutions for indoor positioning have beendeveloped and commercially deployed during the past years. Examplescomprise solutions that are based on pseudolites, which are ground basedGPS-like short-range beacons, ultra-sound positioning solutions,Bluetooth low energy (BLE) based positioning solutions, cellular networkbased positioning solutions and wireless local area network (WLAN) basedpositioning solutions.

A WLAN based positioning solution, for instance, may be divided in twostages, a training stage and a positioning stage. In the training stage,learning data is collected. The data may be collected in the form offingerprints that are based on measurements by mobile devices. Afingerprint may contain a location estimate and measurements taken froma radio interface. The location estimate may be for example GNSS based,sensor-based, or manually inputted. Results of measurements taken fromthe radio interface may comprise, by way of example, measured radiosignal strengths and an identification of WLAN access pointstransmitting the radio signals. Collected fingerprint data may beuploaded to a database in a server or in the cloud, where algorithms maybe run to generate radio models of WLAN access points and/or radio mapsfor positioning purposes. In the positioning stage, the current locationof a mobile device may be estimated based on measurements of the mobiledevice taken from the radio interface and on the data or a subset ofdata that is available from the training stage.

A similar approach could be used for a positioning that is based onother types of terrestrial transmitters or on a combination of differenttypes of terrestrial transmitters.

A model or radio map based positioning may function either inmobile-based or mobile-assisted mode, the difference being in where theposition estimate is calculated. For the mobile-based approach, modeldata or radio map data that has been generated in the training stage maybe transferred to mobile devices by a server as assistance data for usein position determinations. This may be useful for instance for mobilephones, where primarily the mobile device's user is interested inlocation information. The mobile-assisted mode, in contrast, refers tothe case in which the device only makes the appropriate measurements,for e.g. signal strength measurements, and sends the measurement resultsto another entity, e.g. a server, for position estimation.

SUMMARY OF SOME EMBODIMENTS OF THE INVENTION

A method is described, which comprises each of a plurality oftransmitters, which are distributed at fixed locations of a site,transmitting radio signals in regular intervals. The method furthercomprises at least one mesh node performing measurements on radiosignals transmitted by at least one transmitter of the plurality oftransmitters and transmitting messages including results of themeasurements, wherein the at least one mesh node belongs to a pluralityof mesh nodes, with each of the plurality of mesh nodes configured tomonitor at least one environmental parameter at the site. The methodfurther comprises at least one gateway node receiving messagestransmitted by the at least one mesh node directly and/or via at leastone other mesh node of the plurality of mesh nodes, wherein each of theplurality of mesh nodes is configured to receive messages from othermesh nodes of the plurality of mesh nodes and to forward receivedmessages. The method further comprises the at least one gateway nodetransmitting received messages of the at least one mesh node to a serverthat is configured to monitor mesh nodes at the site based on results ofmeasurements in received messages.

Moreover, a first system is described, which comprises means for causingthe system to perform the actions of any presented embodiment of thedescribed method.

The means of this system can be implemented in hardware and/or software.They may comprise for instance processors for executing computer programcode for realizing the required functions, memories storing the programcode, or both. Alternatively, they could comprise for instancecircuitries that are designed to realize the required functions, forinstance implemented in chipsets or chips, like integrated circuits. Inone embodiment, the means of the described first system are processingmeans.

Moreover, a second system is described, which comprises a plurality oftransmitters distributed at fixed locations of a site, each configuredto transmit radio signals in regular intervals. The system furthercomprises a plurality of mesh nodes, each of the plurality of mesh nodesconfigured to monitor at least one environmental parameter at the site,and each of the plurality of mesh nodes configured to receive messagesfrom other mesh nodes of the plurality of mesh nodes and to forwardreceived messages. At least one of the plurality of mesh nodes ismoreover configured to perform measurements on radio signals transmittedby at least one transmitter of the plurality of transmitters and totransmit messages including results of the measurements. The systemfurther comprises at least one gateway node configured to receivemessages transmitted by the at least one mesh node directly and/or viaat least one other mesh node of the plurality of mesh nodes andconfigured to transmit received messages of the at least one mesh nodeto a server that is configured to monitor mesh nodes at the site basedon results of measurements in received messages.

Moreover, at least one non-transitory computer readable storage mediumis described, in which computer program code is stored. The computerprogram code causes a system to perform the actions of any presentedembodiment of the described method when executed by processors.

Each computer readable storage medium could be for example a disk or amemory or the like. The computer program code could be stored in thecomputer readable storage medium in the form of instructions encodingthe computer-readable storage medium. The computer readable storagemedium may be intended for taking part in the operation of a device,like an internal or external hard disk of a computer, or be intended fordistribution of the program code, like an optical disc.

It is to be understood that also the computer program code by itself hasto be considered an embodiment of the disclosure.

In certain embodiments of the described methods, the methods are methodsfor supporting a surveillance of devices at a site. In certainembodiments of the described system, the system is a system forsupporting a surveillance of devices at a site. In certain embodimentsof the described apparatus, the apparatus is an apparatus for supportinga surveillance of devices at a site.

It is to be understood that any feature presented for a particularexemplary embodiment may also be used in an analog manner in combinationwith any other described exemplary embodiment of any category.

Further, it is to be understood that the presentation of the disclosurein this section is merely exemplary and non-limiting.

Other features of the present disclosure will become apparent from thefollowing detailed description considered in conjunction with theaccompanying drawings. It is to be understood, however, that thedrawings are designed solely for purposes of illustration and not as adefinition of the limits of the disclosure, for which reference shouldbe made to the appended claims. It should be further understood that thedrawings are not drawn to scale and that they are merely intended toconceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic block diagram of an example embodiment of a systemaccording to the disclosure;

FIG. 2 is a flow chart illustrating an example operation in the systemof FIG. 1;

FIG. 3 is a schematic block diagram of a further example embodiment ofsystem according to the disclosure;

FIG. 4 is a flow chart illustrating example operations in the system ofFIG. 3;

FIG. 5 is a schematic block diagram of a further example embodiment ofsystem according to the disclosure;

FIG. 6 is a flow chart illustrating example operations in the system ofFIG. 5; and

FIG. 7 is a schematic block diagram of an apparatus.

DETAILED DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic block diagram of an example embodiment of a systemaccording to the disclosure. The system may be arranged at any kind ofsite, for instance a factory or laboratory. The site may comprise indoorand/or outdoor areas.

The system comprises a plurality of mesh nodes 110, a plurality oftransmitters (TX) 120 and at least one gateway node 130. The mesh nodes110 may be assigned to particular locations of the site, or they may bedesigned for frequent rearrangement. They may be configured to operatewhen stationary, or they may be configured to be operable as well whilebeing moved around. The transmitters 120 are distributed to fixedlocations at the site, and each of the transmitters 120 is configured tobroadcast radio signals in regular intervals. Each of the mesh nodes 110is configured to receive messages from other mesh nodes 110 and tobroadcast the received messages. Among the mesh nodes 110, at least onemesh node 111 is moreover configured to perform measurements on radiosignals broadcast by the transmitters 120. The at least one gateway node130 is configured receive messages from any of the mesh nodes 110 and toforward received messages to a server. The server may or may not beconsidered a part of the system and it may or may not be located at thesite. It may even be located at some completely different physicalplace, including the cloud. Any of the transmitters 120 may be atransmitter only or a part of a transceiver. Furthermore, any of thetransmitters 120 may or may be a part of a mesh node 110 of theplurality of mesh nodes or belong to a separate entity. If thetransmitters 120 are part of at least some of the mesh nodes 110, theseat least some mesh nodes 110 are distributed to fixed locations at thesite.

An operation in the system of FIG. 1 will now be described withreference to the flow chart of FIG. 2. The operation is an exampleembodiment of a method according to the disclosure.

Each of a plurality of transmitters 120, which are distributed to fixedlocations of a site, transmits radio signals in regular intervals.(action 210) The transmitters 120 are thus able to generate a staticradio field at the site.

At least one mesh node 111 performs measurements on radio signalstransmitted by at least one transmitter 120 of the plurality oftransmitters 120. The at least one mesh node 111 belongs to a pluralityof mesh nodes 110, with each of the plurality of mesh nodes 110configured to monitor at least one environmental parameter at the site.(action 220) The at least one environmental parameter may comprise forinstance temperature, humidity and/or the presence of dangerous gases,etc. The measurements may be performed for instance regularly orcontinuously or be triggered by a predetermined criterion. Such acriterion may be for instance a change of location detected by at anoptional motion sensor, like an accelerometer, of the mesh node or adetected change of value of the at least one environmental parametermonitored by the mesh node.

The at least one mesh node 111 moreover transmits messages includingresults of the measurements. (action 221) If measurements are performedcontinuously or on a regular basis, messages including results ofmeasurements may be transmitted for instance on a regular basis.Alternatively, even if measurements are performed continuously or on aregular basis, messages including results of measurements may only betransmitted for instance in case a change compared to previous resultsof measurements is detected. Further alternatively, if the measurementsare not performed continuously or on a regular basis, messages includingresults of measurements may be transmitted for instance whenever newmeasurements are available.

At least one gateway node 130 receives messages transmitted by the atleast one mesh node 111 directly and/or via at least one other mesh nodeof the plurality of mesh nodes 110. Each of the plurality of mesh nodes110 is configured to receive messages from other mesh nodes of theplurality of mesh nodes 110 and to forward received messages. (action230) The mesh nodes thus form a wireless mesh—or wireless network—thatenables a relaying of messages between the mesh nodes.

The at least one gateway node 130 transmits received messages of the atleast one mesh node 111 to a server that is configured to monitor meshnodes 110 at the site based on results of measurements in receivedmessages. (action 231)

The disclosure is based on the consideration that at various types ofsites, devices may be employed to monitor environmental parameters ofthe site. At such sites, a comprehensive cellular or WLAN coverage maynot be given. The disclosure is furthermore based on the considerationthat one or more of these devices may be moved and/or deactivated,either in a planned manner or due to reasons unforeseen.

Certain embodiments of the disclosure therefore provide that devicesthat are configured to monitor environmental parameters of the siteconstitute at the same time mesh nodes. At least one of the mesh nodesis enabled to perform measurements on radio signals in the environment.If the radio signals are signals transmitted by transmitters that arearranged at fixed locations at the site, the results of the measurementsallow drawing conclusions on the positions and/or operating states ofone or more mesh nodes. The at least one mesh node is enabled totransmit a message containing the results of the measurements via aradio interface, so that it may be received by one or more of the othermesh nodes and/or by a gateway node. Each of the mesh nodes is enabledto forward a message with results of measurements. The gateway node maythus receive a message with results of measurements from the mesh nodeperforming the measurements directly or via some other mesh nodes. Thegateway node may forward the messages to a server, which may beconfigured to evaluate the measurement results in the messages to obtaindesired information.

Certain embodiments of the disclosure may have the effect thatmonitoring the distribution of nodes may be supported in an efficientmanner when using a mesh formed by the nodes themselves, which ensuresthat measurement results of any mesh node may reach a server via themesh and a gateway node. Monitoring the position and/or the state ofmesh nodes, which in turn monitor at least one environmental parameter,may ensure that values of environmental parameter are determined at theintended locations of a site. It is to be understood that the samemechanism of conveying a message from a mesh node to the server mayefficiently be used as well for messages comprising alternatively or inaddition other content, for instance content relating to the monitoredenvironmental parameters.

Apparatus 100 illustrated in FIG. 1 and the method illustrated in FIG. 2may be implemented and refined in various ways.

The mesh nodes and gateway node may not only be used for conveyingmessages including results of measurements on radio signals performed bymesh nodes. The same approach could be used for conveying messagesincluding results of measurements on radio signals performed by otherdevices that are to be tracked at the site.

In certain embodiments, at least one device performs measurements onradio signals transmitted by at least one transmitter and broadcasts amessage including results of the measurements, wherein the at least onedevice does not belong to the plurality of mesh nodes. At least one meshnode of the plurality of mesh nodes receives the message broadcast bythe at least one device and forwards the received message, wherein eachof the plurality of mesh nodes is configured to receive messagesbroadcast by the at least one device and to forward received messages ofthe at least one device. At least one gateway node receives the messagebroadcast by the at least one device via at least one mesh node of theplurality of mesh nodes. The at least one gateway node transmits themessage broadcast by the at least one device to a positioning serverthat is configured to determine a position of the at least one device atthe site. Determining the position of the device may be based on resultsof measurements in the message of the device. This may have the effectthat a positioning of other devices than mesh nodes may be supported inthe same manner and without any extra effort as the monitoring of meshnodes.

The at least one device in this embodiment may be any device that isdistinct from a mesh node. In particular, it may be any kind of assetdevice. Asset tracking may be relevant e.g. in factories. The assets tobe tracked may be, for example, personnel or expensive equipment. Anissue in factories or at other sites may be the lack of radioconnectivity that is conventionally used for tracking a device. Cellularconnectivity may be intermittent, and WLANs may be missing completely.Thus, the network established with the mesh nodes may be used as wellfor creating a data channel enabling other devices to report results ofmeasurements on radio signals to a server. In an asset tracking usecase, the asset itself does not need to be location-aware; rather, someentity or operator may have to know where the asset is located. Theasset device itself may therefore not be required to have intelligence;it is only required to be configured to take measurements and to sendthem forward.

The results of measurements on radio signals may include in each casefor example an identifier of at least one transmitter transmitting theradio signals and an indication of the received signal strength of radiosignals.

It is to be understood that each transmitter of the plurality oftransmitters may belong to an entity that is provided exclusively forgenerating the static radio field at the site or that it may be part ofan entity that is configured to perform further tasks.

In certain embodiments, all of the transmitters may belong to entitiesother than mesh nodes of the plurality of mesh nodes. They may belongfor instance to Bluetooth™ beacons. This may have the effect that themesh nodes may all be moved freely at the site. The monitoring of meshnodes may comprise in this case for instance determining and monitoringthe position of any mesh node providing measurement results.

In other embodiments, at least some of the transmitters may be a part ofat least some of the plurality of mesh nodes. In this case, thetransmitters may correspond to the transmitters used by the mesh nodesfor transmitting messages containing measurement results, or they may beadditional transmitters of the mesh nodes, for instance Bluetooth™transmitters. This may have the effect that no separate entities arerequired, in case at least some of the mesh nodes are intended tomonitor environmental parameters at more or less permanently fixedlocations of the site anyhow. The monitoring of mesh nodes may comprisethis case for instance determining and monitoring the position of anymesh node providing measurement results and/or determining changes inradio signals of other mesh nodes and to infer therefrom information onthe status of these other mesh nodes.

In certain embodiments, each message comprises information constitutinga message identifier. Each mesh node of the plurality of mesh nodes mayforward a message, if received multiple times, only once based on themessage identifier. Alternatively or in addition, the at least onegateway node may transmit a message, if received multiple times, onlyonce to the server based on the message identifier. This may have theeffect that if mesh nodes or other devices transmit or forward messagesin a broadcast, only a limited number of messages has to be processed bythe forwarding mesh nodes, the at least one gateway and/or the server.

A message identifier of a message containing results of measurements onradio signals transmitted by transmitters may be given for instance by acombination of a time stamp for the measurement results and an identityof the mesh node or any other device generating the message. However, amessage identifier may also be provided in any different manner, as longas it can be assumed to be unique for the site at least for a shortperiod of time. The device identity and/or a time stamp may thenoptionally be included in addition.

In certain embodiments, the server comprises or has access to radio mapdata that has been determined for radio signals transmitted by thetransmitters with their current distribution at the site. The radio mapdata may indicate for instance for each grid point of a virtual gridcovering the area of the site an expected signal strength of radiosignals by each of the plurality of transmitters. Such radio map datamay be assembled based on a survey at the site, which may provideparticularly accurate data, or it may be determined computationallybased on known locations of the transmitters and a known transmissionpower used by the transmitters. The availability of radio map data mayenable the server to compare results of measurements performed by a meshnode or some other device and received in a message with results ofmeasurements that may be expected at various locations of the site todetermine the most likely position of the mesh node or the other device.

In certain embodiments, the server determines a position of the at leastone mesh node based on a received message and stored radio map data foreach of the plurality of transmitters at the site; or stored commonradio map data for all of the plurality of transmitters at the site; orstored information on the current distribution of the plurality oftransmitters and on a predetermined signal strength used by each of theplurality of transmitters.

In certain embodiments, the server may determine in the same manner aposition of at least one device other than a mesh node based on areceived message and a stored radio map data for each of the pluralityof transmitters at the site; or stored common radio map data for all ofthe plurality of transmitters at the site; or stored information on thecurrent distribution of the plurality of transmitters and on apredetermined signal strength used by each of the plurality oftransmitters.

FIG. 3 is a schematic block diagram of a further example embodiment of asystem according to the disclosure. The system supports a monitoring ofmesh nodes and in addition a tracking of assets at a site 300.

The system comprises a plurality of mesh nodes 310, a gateway node 330,an asset device 340 and a server 350 that may optionally be locatedoutside of the site.

The mesh nodes 310 are configured to monitor at least one environmentalparameter at the site, for instance temperature, humidity and/or thepresence of dangerous gases. To this end, they may comprisecorresponding sensors. There may be different mesh node 310 fordifferent parameters or all mesh nodes 310 may be configured to monitorall of the parameters of interest. The mesh nodes 310 are distributed atknown locations in a stationary manner, that is, they are not movedaround in the factory. Each mesh node 310 comprises a transceiverconfigured to transmit and receive radio signals. Furthermore, each meshnode 310 comprises at least one processor and at least one memorystoring computer program code. The at least one processor is configuredto execute computer program code stored in the at least one memory, inorder to cause mesh node 310 to perform desired actions as describedfurther below with reference to the flow chart of FIG. 4. In thisembodiment, no separate transmitters are used; rather, as the mesh nodes310 are assumed to be stationary, they are able to provide the functionof the stationary transmitters themselves. Preferably, though notnecessarily, the mesh nodes 310 are distributed such that at eachlocation of site 300, the radio signals of more than one mesh node 310can be detected.

Gateway node 330 is configured to receive messages from the mesh nodes310 via a radio interface and to forward messages to server 350, forexample via the Internet. To this end, it comprises correspondingcommunication interfaces, at least one processor and at least one memorystoring computer program code. The at least one processor is configuredto execute computer program code stored in the at least one memory, inorder to cause gateway node 330 to perform desired actions as describedfurther below with reference to the flow chart of FIG. 4.

Server 350 may be a data aggregating analytics and positioning server.Server 350 comprises a communication interface that enables acommunication with other devices, for instance via the Internet. Server350 comprises or has access to a memory of a database storing radio mapdata at least for site 300. The radio map data may be mapped to avirtual grid covering the area of the site. It may provide for each gridpoint (or for each grid area) the identities (IDs) of mesh nodes 310, ofwhich radio signals may be expected to be detected at a location of thesite corresponding to the grid point, and an indication of the expectedsignal strength of the radio signals. Server 350 comprises at least oneprocessor and at least one memory storing computer program code. The atleast one processor is configured to execute computer program codestored in the at least one memory, in order to cause gateway node 330 toperform desired actions as described further below with reference to theflow chart of FIG. 4.

Asset device 340 may be a device that is meant to be attached to orintegrated into a larger mobile entity, or a device that is configuredto be carried by a user, e.g. in the form of a handheld device, abracelet or a badge. Asset device 340 comprises a transceiver configuredto transmit and receive radio signals. Furthermore, asset device 340comprises at least one processor and at least one memory storingcomputer program code. The at least one processor is configured toexecute computer program code stored in the at least one memory, inorder to cause asset device 340 to perform desired actions as describedfurther below with reference to FIG. 4.

Example operations in the system of FIG. 3 will now be described withreference to the flow chart of FIG. 4.

The transmitter part (TX) of the transceivers of all mesh nodes 310periodically broadcast radio signals with a constant power to provide astatic radio signal field, that is, a field that is not changingessentially over time. Changes may in particular be due to rearrangementof equipment at the site, etc. The radio signals convey a respectiveprobe message which comprises an identifier (ID) for the transmittingmesh node 310. The probe message may be differentiated from othermessages e.g. in that it comprise a probe indication or by using adedicated predetermined frequency or the like. (action 410) After thedeployment of the mesh nodes 310 and the activation of the periodictransmissions and before other actions presented in the following withreference to FIG. 4 are started, fingerprints may be collectedthroughout the site 300 as a basis for a generation of radio map datarepresenting the static radio signal field. The radio map data may thenbe stored for further use in server 350.

Once radio map data has been generated and stored in server 350, allmesh nodes 310 that are to be monitored and all asset devices 340 thatare to be tracked perform in parallel to the broadcasts measurements onradio signals conveying the probe messages and received by means oftheir transceiver or receiver. Both types of devices will also bereferred to as originating devices. The measurements result in receivedsignal strength (RSS) values. Alternatively, they could result inreceived signal strength indicators (RSSI). In addition, the ID of thetransmitting mesh node 310 is extracted from the probe message. (action420) The measurements may be performed for example either constantly oron a regular basis, in the latter case using a duration that exceeds theperiod of the periodic transmission of the probe messages in action 410.It is to be understood that the regular basis may be defined to varyover time; there could be for instance different intervals for daytimeand nighttime.

The originating devices assemble a message including at least the latestmeasurement results for all (other) mesh nodes 310 in detection rangeand a message identifier (ID) in regular intervals. The message ID maybe for instance in the form of a device ID and a time stamp, acomputational combination thereof, or some other unique value. In thelatter case, device ID and time stamp may be included in addition in themessage. (action 421) It is to be understood that an originating devicemay add any other information that is to be conveyed to server 350 tothe message. For instance, if the originating device is a mesh node 310,the originating device may periodically determine the value of one ormore parameters by means of one or more sensors, and include the latestvalue or values in the message. If preferred, however, such parametervalues could also be transmitted in separate messages.

The originating devices 310, 340 then broadcast the assembled messages.(action 422)

Equally in parallel, all mesh nodes 310 operate as forwarding meshnodes. In this function, they receive messages including measurementsthat have been broadcast by nearby asset devices 340 or other mesh nodes310. (action 430)

Some messages may reach a forwarding mesh node 310 multiple times, thatis, directly from the originating device 310, 340 and/or from one ormore intermediate forwarding mesh nodes 310. Therefore, each forwardingmesh node 310 extracts and evaluates the message IDs in the receivedmessages and discards duplicate messages based on the IDs. (action 431)

The forwarding mesh nodes 310 then broadcast the respective firstmessage for each message ID via the radio interface using itstransceiver. (action 432)

Equally in parallel, gateway node 330 receives broadcast messagesincluding measurement results via the radio interface from originatingdevices 310, 340 and/or from forwarding mesh nodes 310. (action 440)

Similarly as the forwarding mesh nodes 310, gateway node 330 extractsand evaluates the message IDs in the received messages and discardsduplicate messages based on the contained message IDs. (action 441)

Gateway node 330 then transmits the respective first message for eachmessage ID via the Internet specifically to server 350. (action 442)

An example path of a first message including measurement results fromasset device 340 (as an example originating device) to server 350 isindicated in FIG. 3 with bold arrows 360. While the message from assetdevice 340 may take multiple paths via various mesh nodes 310, only thefirst one arriving at gateway node 330 shall be forwarded to server 350.

Server 350 receives each message including measurement results via theInternet. Each message is received only once. (action 450) In somealternative embodiments, more than one gateway node could be provided toenhance robustness of the system by providing redundancy. In this case,server 350 receives each message at the most as many times as there aregateway nodes.

Server 350 then determines a position of each originating device 310,340. The position is determined for an originating device identified bya device ID in the message. The position is determined based onmeasurement results in the form of RSS values and associated mesh nodeIDs contained in the message and based on stored radio map data. (action451)

Server 350 may then inform an internal or external application about aposition of any asset device 340 for which a position has beendetermined as originating device. (action 452) The position can be usedfor instance for purposes of tracking, analytics, safety, etc. As assetdevice 340 may not have to know its location, the positioning can takeplace without return path to asset device 340.

In addition, server 350 may detect changes in the positions of the meshnodes 310. The mesh nodes 310 are assumed to be stationary, and if achange in position is detected for a mesh node 310, the radio fieldgenerated with the probe messages of the mesh nodes 310 can be assumedto be disturbed. As a result, the stored radio map data representing theprevious radio field may have to be updated, as otherwise thepositioning of asset devices 340 may be affected adversely. Therefore,server 350 may alert a system operator if any change in position of themesh nodes 310 is detected. (action 452) It is to be understood thatalerting a system operator may not only be based on detected changes ofpositions of originating mesh nodes 310. For an additional oralternative approach, server 350 may store for instance in additioninformation indicating for each mesh node 310 which received signalstrength it should measure for signals of which neighboring mesh nodes310. If there is a significant discrepancy between an expected RSS valueand a measured RSS value indicated in a message (or in case of anabsence of an expected RSS value in a message), the system operator maybe alerted too.

Alerting a system operator in action 452 whenever changes in the meshnode deployment are detected also ensures that potential irregularitiesin the monitoring of environmental parameters at site 300 are detected.

If any of the messages that are forwarded to server 350 also containenvironmental parameter values, server 350 may equally be configured toevaluate these parameter values. It could alert a system operator, forinstance, in case some parameter value provided by a mesh node 310 at aknown position of site 300 exceeds a predetermined threshold value forthis parameter in an area comprising this position.

FIG. 5 is a schematic block diagram of a further example embodiment of asystem according to the disclosure. The system supports again apositioning of mesh nodes and assets at a site 500.

The system comprises a plurality of mesh nodes 510, a plurality ofBluetooth™ beacons 520, a gateway node 530, an asset device 540 and aserver 550 that may be located outside of the site 500.

Mesh nodes 510, gateway node 530, asset device 540 and server 550 may besimilar to the corresponding entities of the system of FIG. 3, exceptthat in this embodiment, the mesh nodes 510 do not have to be confinedto fixed locations.

Instead, the Bluetooth™ beacons 520 are located at fixed, knownpositions. Each Bluetooth™ beacon 520 comprises a transmitter configuredto transmit radio signals. Preferably, though not necessarily, theBluetooth™ beacons 520 are distributed such that at each location ofsite 500, the radio signals of more than one Bluetooth™ beacon 520 canbe detected.

Example operations in the system of FIG. 5 will now be described withreference to the flow chart of FIG. 6.

The operations are similar to the operations in the system of FIG. 3described with reference to the flow chart of FIG. 4, and onlydifferences will be presented.

All Bluetooth™ beacons 520 periodically broadcast radio signals withconstant power to provide a static radio signal field, that is, a fieldthat is not changing essentially over time. The radio signals are in theform of a probe message which comprises an identifier (ID) for thetransmitting Bluetooth™ beacon 520. The probe messages may bedifferentiated from messages of other devices 510, 540 in the systeme.g. in that they comprise a probe indication or by using a dedicatedpredetermined frequency or the like. (action 610)

The radio signals are detected and processed by mesh nodes 510 and assetdevices 540 in the same manner as described with reference to actions420-422 of FIG. 4 to generate—as originating devices—messages withmeasurement results that are conveyed partly via one or more mesh nodes510 and via gateway node 530 to server 550, as described with referenceto actions 430-432 of FIG. 4. (actions 620-642)

An example path of a first message including measurement results fromasset device 540 (as an example originating device) to server 550 isindicated in FIG. 5 with bold arrows 560. Server 550 receives messagesincluding measurement results via the Internet. Each message is receivedonly once. (action 650) If more than one gateway node is provided in avariation of the system, server 550 receives each message at the most asmany times as there are gateway nodes.

Server 550 then determines a position of each originating device 510,540. The position is determined for an originating device as identifiedby a device ID in the message. The position is determined for eachoriginating device 510, 540 based on RSS values and associatedBluetooth™ beacon IDs contained in the message and based on stored radiomap data. (action 651)

Server 550 may then inform internal and/or external applications about aposition of any mesh node 510 and any asset device 540 for which aposition has been determined as originating device. (action 652)

In the embodiment of FIGS. 5 and 6, changes in the distribution of themesh nodes 510 do not have any effect on the static radio signal field.The mesh nodes 510 are only responsible for monitoring environmentalparameters and for forwarding positioning related messages to gatewaynode 530. Thus, the mesh nodes 510 may be moved freely at the site asneeded for the respective monitoring task; and as long as any mesh nodecan communicate with at least one other node (mesh node or gatewaynode), the messages can be relayed to gateway node 530.

If the messages that are forwarded to server 550 also containenvironmental parameter values, server 550 may equally evaluate theseparameter values. It could track the evolvement of parameter values overtime and/or alert a system operator, for instance, in case someparameter value provided by a mesh node 510 at a determined position ofsite 500 exceeds a predetermined threshold value for this parameter inan area comprising this position.

It is to be understood that the presented example systems may be variedin many ways by adding, omitting and/or modifying components; and thatthe presented example operations may be varied in many ways by adding,omitting and/or modifying actions and/or by changing the order ofactions.

For instance, in the flow chart of FIG. 4, actions 451-452, at firstonly the distribution of mesh nodes 310 could be checked and possibly analert being output to a system operator. The position of an asset device340 may then be determined only after it has been ensured that thedistribution of mesh nodes 310 is as assumed for the stored radio mapdata.

For instance, in the flow charts of FIGS. 4 and 6, the mesh nodes do nothave to broadcast messages. Alternatively, they may transmit messagesonly to those mesh nodes and gateway nodes that have been detected to bein a communication range. They may also relay messages to subsequentmesh nodes more or less randomly, for instance to a certain maximumnumber of neighboring nodes, like two or three nodes withincommunication range.

For instance, in a variation of the system of FIG. 3, only some of themesh nodes 310 may be assumed to be stationary, while the other meshnodes 310 may be allowed to move freely at site 300. In this case, onlythe stationary mesh nodes 310 may be configured to broadcast probemessages on a regular basis to generate a certain radio field, while allor only the remaining mesh nodes 310 perform measurements on the radiosignals and broadcast the measurement results in messages. However, alsoin this case, all of the mesh nodes 310 may be configured to forwardreceived messages so that they eventually reach gateway node 330 andthus server 350.

For instance, in a variation of the system of FIG. 3 or FIG. 5,different servers may be used for different tasks, like positioningpurposes and environmental parameter surveilling purposes. The gatewaynodes may be configured in this case to forward messages that have beenmarked accordingly to the appropriate server.

Each of the presented entities of FIGS. 1, 3 and 5, including meshnodes, asset devices, gateway nodes, servers and Bluetooth™ beacons (orother entities comprising a transmitter), may be caused to perform theindicated actions by at least one processor executing computer programcode stored in at least one memory of the entity.

An example general structure of any such entity is presented in theblock diagram of FIG. 7.

Entity 700 comprises at least one processor 701, at least onenon-volatile memory 702, at least one volatile memory 705 and at leastone communication interface or communication module 706.

The at least one processor 701 is linked to each of the othercomponents; it may be enabled for instance to access each of the othercomponents by means of a data bus 707.

The at least one non-volatile memory 702 may comprise for instance aread only memory (ROM). It may store an operating system (OS) 703 andsoftware applications 704 including computer program code to be executedby the at least one processor 701 in order to cause entity 700 toperform desired actions.

The at least one volatile memory 705 may be for instance a random accessmemory (RAM). The at least one processor 701 may use volatile memory 705as a working memory.

The at least one communication interface or communication module 706enables all external communications required for the operation of theconcerned entity. For instance, if entity 700 is a Bluetooth™ beacon,the at least one communication interface or communication module 706comprises at least a Bluetooth™ transmitter. For instance, if entity 700is a mesh node, the at least one communication interface orcommunication module 706 comprises a transceiver that is configured toreceive signals from other mesh nodes and from asset devices, and thatis configured to transmit signals to other mesh nodes and to a gatewaynode. For instance, if entity 700 is an asset device, the at least onecommunication interface or communication module 706 comprises atransceiver that is configured to enable a communication with mesh nodesand optionally with a gateway node. If the system makes use ofBluetooth™ beacons for generating the static radio signal field, the atleast one communication interface or communication module 706 of assetdevices and mesh nodes comprise in addition a Bluetooth™ transceiver orat least a Bluetooth™ receiver. For instance, if entity 700 is a gatewaynode, the at least one communication interface or communication module706 comprises a receiver or transceiver that is configured to enablereceipt of radio signals from mesh nodes and optionally from assetdevices. In addition, it comprises an interface 706 enabling access to aserver, for instance a TCP/IP socket enabling an access to a server viathe Internet. For instance, if entity 700 is a server, it comprises aninterface 706 enabling a communication with a gateway node, for instancea TCP/IP socket enabling an access via the Internet. In addition, it maycomprise a data interface 706 for accessing an external database storingradio map data or other required information in a memory. The radiosignal based communication between asset devices, mesh nodes and gatewaynode may take place for instance according to standard IEEE 802.15.4 oraccording to any proprietary communication protocol.

If entity 700 is a mesh node, it may comprise in addition at least onesensor 710, for instance a temperature sensor, a humidity sensor or agas sensor.

If entity 700 is a server, the at least one memory 702 may store inaddition radio map data 720 or other data. In general, the at least onememory 702 may store any data that may be needed by an entity 700.

Entity 700 could comprise various other components, like a batteryand/or a mains connection, a user interface, etc. Processor(s) 701 andmemories 702 and 705 may optionally belong to a chip or a circuitry,like an integrated circuit, which may comprise in addition various othercomponents, for instance a further processor or memory.

In an example embodiment, entity or module 700 of FIG. 7 may representan apparatus comprising at least one processor 701 and at least onememory 702 storing computer program code 703, wherein the at least onememory 702 and the computer program code 703, with the at least oneprocessor 701, configured to cause a mesh node to: monitor at least oneenvironmental parameter; perform measurements on radio signalstransmitted by at least one transmitter, the least one transmitter beingat least one of a plurality of transmitters distributed at fixedlocations at a site and transmitting radio signals in regular intervals;transmit messages including results of the measurements; and receive andforward messages including results of measurements at other mesh nodes.The apparatus may be the mesh node or at least one component of the meshnode, like a chip or chipset or any other kind of circuitry,

FIGS. 2, 4 and 6 may also be understood to represent exemplaryfunctional blocks of a computer program code for supporting asurveillance of a site.

Summarized, certain embodiments of the disclosure may enable the use ofmesh nodes for a plurality of different tasks. They may be used formonitoring one or more environmental parameter values at a site. Theymay be used for forming a communication network that is suited forforwarding results of the monitoring at any location of the site to agateway node and thus to a server. The network of mesh nodes mayfurthermore be used for supporting a positioning of separate assetdevices by forwarding messages of such asset devices via the gatewaynode to the server. And finally, the network of mesh nodes may be usedfor supporting a surveillance of the distribution of the mesh nodesthemselves by forwarding messages containing results of measurement onradio signals performed at mesh nodes via the gateway node to theserver. Using the mesh network concept may have the effect that there isno need to deploy any other connectivity mechanisms, such as WLAN orcellular, at the site for conveying the measurement results to a server.The mesh network may also be particularly robust, because there may beno single point of failure when assuming that each node (mesh node orgateway node) sees more than one other node. Both, asset devices andmesh nodes may be positioned with an accuracy of 2-3 meters and withcoverage of basically 100%.

The following embodiments of the disclosure are also disclosed:

Embodiment 1

A method comprising:

-   -   each of a plurality of transmitters, which are distributed at        fixed locations of a site, transmitting radio signals in regular        intervals;    -   at least one mesh node performing measurements on radio signals        transmitted by at least one transmitter of the plurality of        transmitters and transmitting messages including results of the        measurements, wherein the at least one mesh node belongs to a        plurality of mesh nodes, with each of the plurality of mesh        nodes configured to monitor at least one environmental parameter        at the site;    -   at least one gateway node receiving messages transmitted by the        at least one mesh node directly and/or via at least one other        mesh node of the plurality of mesh nodes, wherein each of the        plurality of mesh nodes is configured to receive messages from        other mesh nodes of the plurality of mesh nodes and to forward        received messages; and    -   the at least one gateway node transmitting received messages of        the at least one mesh node to a server that is configured to        monitor mesh nodes at the site based on results of measurements        in received messages.

Embodiment 2

The method according to embodiment 1, further comprising:

-   -   at least one device performing measurements on radio signals        transmitted by at least one transmitter and broadcasting a        message including results of the measurements, wherein the at        least one device does not belong to the plurality of mesh nodes;    -   at least one mesh node of the plurality of mesh nodes receiving        the message broadcast by the at least one device and forwarding        the received message, wherein each of the plurality of mesh        nodes is configured to receive messages broadcast by the at        least one device and to forward received messages of the at        least one device;    -   at least one gateway node receiving the message broadcast by the        at least one device via at least one mesh node of the plurality        of mesh nodes; and    -   the at least one gateway node transmitting the message broadcast        by the at least one device to a positioning server that is        configured to determine a position of the at least one device at        the site.

Embodiment 3

The method according to embodiment 1 or 2, wherein the transmitters

-   -   belong to entities other than mesh nodes of the plurality of        mesh nodes; and/or    -   belong to Bluetooth™ beacons.

Embodiment 4

The method according to embodiment 1 or 2, wherein at least some of thetransmitters are a part of at least some of the plurality of mesh nodes.

Embodiment 5

The method according to any of embodiments 1 to 4,

-   -   wherein each message comprises information constituting a        message identifier; and    -   wherein each mesh node of the plurality of mesh nodes forwards a        message, if received multiple times, only once based on the        message identifier.

Embodiment 6

The method according to any of embodiments 1 to 5,

-   -   wherein each message comprises information constituting a        message identifier; and    -   wherein the at least one gateway node transmits a message, if        received multiple times, only once to the server based on the        message identifier.

Embodiment 7

The method according to any of embodiments 1 to 6, wherein the servercomprises or has access to radio map data that has been determined forradio signals transmitted by the transmitters with their currentdistribution at the site.

Embodiment 8

The method according to any of embodiments 1 to 7, further comprisingthe server determining a position of the at least one mesh node based ona received message and

-   -   stored radio map data for each of the plurality of transmitters        at the site; or    -   stored common radio map data for all of the plurality of        transmitters at the site; or    -   stored information on the current distribution of the plurality        of transmitters and on a predetermined signal strength used by        each of the plurality of transmitters.

Embodiment 9

The method according to embodiment 2 or any of embodiments 3 to 8 as faras referring back to embodiment 2, further comprising the serverdetermining a position of the at least one device based on a receivedmessage and

-   -   stored radio map data for each of the plurality of transmitters        at the site; or    -   stored common radio map data for all of the plurality of        transmitters at the site; or    -   stored information on the current distribution of the plurality        of transmitters and on a predetermined signal strength used by        each of the plurality of transmitters.

Embodiment 10

A system comprising:

-   -   a plurality of transmitters distributed at fixed locations of a        site, each configured to transmit radio signals in regular        intervals;    -   a plurality of mesh nodes, each of the plurality of mesh nodes        configured to monitor at least one environmental parameter at        the site, each of the plurality of mesh nodes configured to        receive messages from other mesh nodes of the plurality of mesh        nodes and to forward received messages, and at least one of the        plurality of mesh nodes configured to perform measurements on        radio signals transmitted by at least one transmitter of the        plurality of transmitters and to transmit messages including        results of the measurements; and    -   at least one gateway node configured to receive messages        transmitted by the at least one mesh node directly and/or via at        least one other mesh node of the plurality of mesh nodes and        configured to transmit received messages of the at least one        mesh node to a server that is configured to monitor mesh nodes        at the site based on results of measurements in received        messages.

Embodiment 11

The system according to embodiment 10,

-   -   wherein each of the plurality of mesh nodes is further        configured to receive messages broadcast by at least one device        that does not belong to the plurality of mesh nodes and to        forward received messages of the at least one device, wherein        the messages include results of measurements performed by the at        least one device on radio signals transmitted by at least one        transmitter; and    -   wherein the at least one gateway node is further configured to        receive the messages broadcast by the at least one device via at        least one mesh node of the plurality of mesh nodes and to        transmit the messages broadcast by the at least one device to a        positioning server that is configured to determine a position of        the at least one device at the site.

Embodiment 12

The system according to embodiment 10 or 11, wherein the transmitters

-   -   belong to entities other than mesh nodes of the plurality of        mesh nodes; and/or    -   belong to Bluetooth™ beacons.

Embodiment 13

The system according to embodiment 10 or 11, wherein at least some ofthe transmitters are a part of at least some of the plurality of meshnodes.

Embodiment 14

The system according to any of embodiments 10 to 13,

-   -   wherein each message comprises information constituting a        message identifier; and    -   wherein each mesh node of the plurality of mesh nodes is        configured to forward a message, if received multiple times,        only once based on the message identifier.

Embodiment 15

The system according to any of embodiments 10 to 14,

-   -   wherein each message comprises information constituting a        message identifier; and    -   wherein the at least one gateway node is configured to transmit        a message, if received multiple times, only once to the server        based on the message identifier.

Embodiment 16

The system according to any of embodiments 10 to 15, further comprisingthe server, wherein the server comprises or has access to radio map datathat has been determined for radio signals transmitted by thetransmitters with their current distribution at the site.

Embodiment 17

The system according to any of embodiments 10 to 16, further comprisingthe server, wherein the server is configured to determine a position ofthe at least one mesh node based on a received message and

-   -   stored radio map data for each of the plurality of transmitters        at the site; or    -   stored common radio map data for all of the plurality of        transmitters at the site; or    -   stored information on the current distribution of the plurality        of transmitters and on a predetermined signal strength used by        each of the plurality of transmitters.

Embodiment 18

The system according to embodiment 11 or any of embodiments 12 to 17 asfar as referring back to embodiment 11, further comprising the server,wherein the server is configured to determine a position of the at leastone device based on a received message and

-   -   stored radio map data for each of the plurality of transmitters        at the site; or    -   stored common radio map data for all of the plurality of        transmitters at the site; or    -   stored information on the current distribution of the plurality        of transmitters and on a predetermined signal strength used by        each of the plurality of transmitters.

Embodiment 19

An apparatus comprising at least one processor and at least one memorystoring computer program code, wherein the memory and the computerprogram code, with the processor, configured to cause a mesh node to:

-   -   monitor at least one environmental parameter;    -   perform measurements on radio signals transmitted by at least        one transmitter, the least one transmitter being at least one of        a plurality of transmitters distributed at fixed locations at a        site and transmitting radio signals in regular intervals;    -   transmit messages including results of the measurements; and    -   receive and forward messages including results of measurements        at other mesh nodes.

Any presented connection in the described embodiments is to beunderstood in a way that the involved components are operationallycoupled. Thus, the connections can be direct or indirect with any numberor combination of intervening elements, and there may be merely afunctional relationship between the components.

Further, as used in this text, the term ‘circuitry’ refers to any of thefollowing:

(a) hardware-only circuit implementations (such as implementations inonly analog and/or digital circuitry) and (b) to combinations ofcircuits and software (and/or firmware), such as (as applicable): (i) toa combination of processor(s) or (ii) to portions ofprocessor(s)/software (including digital signal processor(s)), software,and memory(ies) that work together to cause an apparatus, such as amobile phone or server, to perform various functions) and (c) tocircuits, such as a microprocessor(s) or a portion of amicroprocessor(s), that requires software or firmware for operation,even if the software or firmware is not physically present.

This definition of circuitry applies to all uses of this term in thisapplication, including in any claims. As a further example, as used inthis application, the term circuitry also covers an implementation ofmerely a processor (or multiple processors) or portion of a processorand its (or their) accompanying software and/or firmware. The termcircuitry also covers, for example and if applicable to the particularclaim element, a baseband integrated circuit or applications processorintegrated circuit for a mobile phone or a similar integrated circuit inserver, a cellular network device, or other network device.

Any of the processors mentioned in this text could be a processor of anysuitable type. Any processor and memory may comprise but is not limitedto one or more single-core processor(s), one or more dual-coreprocessor(s), one or more multi-core processor(s), one or moremicroprocessor(s), one or more digital signal processor(s), one or moreprocessor(s) with accompanying digital signal processor(s), one or moreprocessor(s) without accompanying digital signal processor(s), one ormore special-purpose computer chips, one or more field-programmable gatearrays (FPGAS), one or more controllers, one or moreapplication-specific integrated circuits (ASICS), or one or morecomputer(s). The relevant structure/hardware has been programmed in sucha way to carry out the described function.

Any of the memories mentioned in this text could be implemented as asingle memory or as a combination of a plurality of distinct memories,and may comprise for example a read-only memory, a random access memory,a flash memory or a hard disc drive memory etc.

Moreover, any of the actions described or illustrated herein may beimplemented using executable instructions in a general-purpose orspecial-purpose processor and stored on a computer-readable storagemedium (e.g., disk, memory, or the like) to be executed by such aprocessor. References to ‘computer-readable storage medium’ should beunderstood to encompass specialized circuits such as FPGAs, ASICs,signal processing devices, and other devices.

It will be understood that all presented embodiments are only exemplary,that features of these embodiments may be omitted or replaced and thatother features may be added. Any mentioned element and any mentionedmethod step can be used in any combination with all other mentionedelements and all other mentioned method step, respectively. It is theintention, therefore, to be limited only as indicated by the scope ofthe claims appended hereto.

What is claimed is:
 1. A method for surveillance of a site location, themethod comprising: receiving a message from a gateway device, themessage including at least one identifier, data indicative ofmeasurements of radio signals, and at least one environmental parametercollected by a mesh device of a plurality of mesh devices located at anarea for the site location, the plurality of mesh devices configured torelay messages between the plurality of mesh devices; accessing a storedradio map, in response to the message, that covers the area of the sitelocation including the mesh device; and calculating a position of themesh device based on the measurements of the radio signals, wherein theposition of the mesh device is determined based on the stored radio map.2. The method of claim 1, wherein the mesh device is configured toremain in a stationary status, the method further comprising: generatingan alert in response to a change in the position of the mesh device; andupdating the stored radio map according to the change in the position ofthe mesh device.
 3. The method of claim 1, further comprising: comparingthe measurements of the radio signals to an expected value; andgenerating an alert in response to the comparison.
 4. The method ofclaim 1, further comprising: determining an irregularity in the at leastone environmental parameter; and generating an alert in response to theirregularity.
 5. The method of claim 1, wherein the gateway device isincluded in a plurality of gateway devices and the message is includedin a plurality of messages, wherein each of the plurality of messagescorresponds to one of the plurality of gateway devices.
 6. The method ofclaim 1, wherein the stored radio map includes a grid covering ageographic area for the site.
 7. An apparatus for surveillance of asite, the apparatus comprising: a memory configured to store a radiomap; a communication interface configured to receive a message from agateway device, the message including at least one identifier and dataindicative of measurements of radio signals; and at least one processorconfigured to calculate a position of at least one mesh device based onthe measurements of the radio signals, wherein the at least oneprocessor is configured to calculate the position of the at least onemesh device based on the stored radio map, the at least one mesh deviceconfigured to relay messages in a mesh network of mesh devices.
 8. Theapparatus of claim 7, wherein the at least one processor is configuredto generate an alert.
 9. The apparatus of claim 7, wherein the at leastone device includes a mesh device configured to remain in a stationarystatus, and wherein an alert is generated in response to a change in theposition of the mesh device and the stored radio map is updatedaccording to the change in the position of the mesh device.
 10. Theapparatus of claim 8, wherein the alert is based on a comparison of themeasurements of the radio signals to an expected value.
 11. Theapparatus of claim 8, wherein the alert is based on an irregularity inat least one environmental parameter included in the message.
 12. Theapparatus of claim 7, wherein a quantity of gateway devices includingthe gateway device corresponds to a quantity of messages include themessage.
 13. A non-transitory computer-readable medium storing computerprogram code, the computer program code when executed by a processorcausing an apparatus to perform: receiving a message from a gatewaydevice, the message including at least one identifier and dataindicative of measurements of radio signals from at least onetransmitter, the least one transmitter being at least one of a pluralityof transmitters distributed at fixed locations at a site; accessing astored radio map in response to the message; calculating a position ofat least one device based on the measurements of the radio signals,wherein the position of the at least one device is determined based onthe stored radio map and the stored radio map includes a grid covering ageographic area for the sit; wherein the at least one device includes amesh device configured to remain in a stationary status, the mesh deviceconfigured to relay messages in a network of mesh devices; andgenerating an alert in response to the position of the at least onedevice.
 14. The non-transitory computer-readable medium of claim 13,wherein the at least one device includes the at least one transmitter.15. The non-transitory computer-readable medium of claim 13, wherein theat least one device includes a mesh device and an asset device.
 16. Thenon-transitory computer-readable medium of claim 13, wherein thecomputer program code when executed by the processor further causes theapparatus to perform: generating an alert in response to a change in theposition of the mesh device; and updating the stored radio map accordingto the change in the position of the mesh device.
 17. The method ofclaim 1, wherein the radio map comprises predetermined signal strengthsof the radio signals within the site.
 18. The apparatus of claim 7,wherein the radio map comprises predetermined signal strengths of theradio signals within the site.
 19. The non-transitory computer-readablemedium of claim 13, wherein the radio map comprises predetermined signalstrengths of the radio signals within the site.